<?php

class EmailAddressValidator
{
	public function Validate($Value)
	{
		if($this->validEmail($Value))
			return null;
		return 'Not a valid email address.';
	}
	
	/**
	Validate an email address.
	Provide email address (raw input)
	Returns true if the email address has the email 
	address format and the domain exists.
	*/
	function validEmail($email)
	{
	   $isValid = true;
	   $atIndex = strrpos($email, "@");
	   if (is_bool($atIndex) && !$atIndex)
	   {
	      $isValid = false;
	   }
	   else
	   {
	      $domain = substr($email, $atIndex+1);
	      $local = substr($email, 0, $atIndex);
	      $localLen = strlen($local);
	      $domainLen = strlen($domain);
	      if ($localLen < 1 || $localLen > 64)
	      {
	         // local part length exceeded
	         $isValid = false;
	      }
	      else if ($domainLen < 1 || $domainLen > 255)
	      {
	         // domain part length exceeded
	         $isValid = false;
	      }
	      else if ($local[0] == '.' || $local[$localLen-1] == '.')
	      {
	         // local part starts or ends with '.'
	         $isValid = false;
	      }
	      else if (preg_match('/\\.\\./', $local))
	      {
	         // local part has two consecutive dots
	         $isValid = false;
	      }
	      else if (!preg_match('/^[A-Za-z0-9\\-\\.]+$/', $domain))
	      {
	         // character not valid in domain part
	         $isValid = false;
	      }
	      else if (preg_match('/\\.\\./', $domain))
	      {
	         // domain part has two consecutive dots
	         $isValid = false;
	      }
	      else if (!preg_match('/^(\\\\.|[A-Za-z0-9!#%&`_=\\/$\'*+?^{}|~.-])+$/',
	                 str_replace("\\\\","",$local)))
	      {
	         // character not valid in local part unless 
	         // local part is quoted
	         if (!preg_match('/^"(\\\\"|[^"])+"$/',
	             str_replace("\\\\","",$local)))
	         {
	            $isValid = false;
	         }
	      }
	      if ($isValid && !(checkdnsrr($domain,"MX") || checkdnsrr($domain,"A")))
	      {
	         // domain not found in DNS
	         $isValid = false;
	      }
	   }
	   return $isValid;
	}
}